Bun adds built-in bun lint and bun fmt: reads ESLint/Prettier configs, 1,021 rules, 2.9s vs Prettier's 295s CPU on vscode format check

Bun merged PR #44805 on Oct 12, adding two native commands. bun lint implements 1,021 rules from ESLint, typescript-eslint, React, import, unicorn, jsx-a11y and more, reads existing ESLint or oxlint configs, runs type-aware rules without the typescript package, and supports --fix. bun format (alias bun fmt) reads Prettier or oxfmt configs and aims for byte-identical output across JS/TS/JSX, CSS/SCSS/Less, HTML, Vue, Angular, JSON, YAML, TOML, Markdown, MDX and GraphQL, and sorts imports, Tailwind classes and package.json. Both use every core, need no packages, and are configured in bunfig.toml; an existing lint or format script keeps its old meaning.

Vendor-reported results: 69,640 ESLint rule-test cases and 27,702 oxlint cases with zero failures; 9,728 of Prettier's format tests pass with 5 failures; across 330 real repositories, output matches oxfmt in 95% of runs and Prettier in 77%. On vscode's src (10,149 files), a format check takes 2.9s of CPU time versus 5.5s for oxfmt, 20s for Biome and 295s for Prettier 3.9.9; linting with vscode's own ESLint config took 15.8s versus 404s (measured on an earlier build). With heavy third-party JS plugins the median gain over ESLint drops to 1.7x, and the binary grows by about 15MB.

The commands are in main and documented at bun.com/docs/format and bun.com/docs/lint, but the latest stable release, v1.4.3, does not include them yet. Use bun fmt --check in CI (exit codes 0/1/2), bun fmt --init to create config, and diff against your current Prettier/ESLint output before switching.